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CALCULATION NOTES <br />Subject By <br />Checked <br />• Acct <br />19 <br />General Data <br />Storm Runoff Computations (Continued) <br />Volume of Runoff: <br />Sheet No. 3 of 4 Sheets <br />V = Acres x Q (inches) 12 = Acre - feet. <br />Vl = Acre-feet x 43560 = cubic-feet. <br />i <br />Acres <br />Alanimetered areas on referenced maps. <br />Areas planimetered 3 to 4 times and averaged. <br />Reduction to Acres = (Scale)2 x sq. in. _ <br />43560 <br />~ Soil Loss Volumes: <br />Universal Soil Loss Equation (USLE) <br />A = RKLSC <br />F: <br />A = The computed soil loss per unit area expressed in tons per acre <br />per year. <br />i R = The rainfall and runoff factor = 38 <br />i Figure 1. Average annual values of the rainfall erosion index. <br />~ Predicting Rainfall Erosion Losses. Agriculture Handbook N537, and <br />~ USLE- Factor R, Fig. 7, pg. 27, "Erosion & Sediment Control- Colorado" <br />Interim Guide. <br />i K = The soil erodibility factor. Some values used are as follows: <br />Soil B = 0.43 <br />' Gravel Yards & Roads 0.25 <br />' Coal, fine coal on stockpile area surface 0.70 <br />Refuse waste 0.17 <br />Others if used will be stated in individual area calculations. <br />LS = The factor that accounts for the length and percent slope. Tables <br />from Interim Guide, Fig. 9. <br />C = The soil cover factor. Interim Guide, Fig. 10 or 11, Agri. Handbook <br />' N537. <br />• <br />B-4 <br />